Method of improving rate of ammonia development of light sensitive diazotype materials



2,755,185 Patented July 17, 1956 METHOD OF IMPROVING RATE OF AMMONIA DEVELOPMENT OF LIGHT SENSITIVE DIAZO- TYPE MATERIALS John Sulich, Jr., Endicott, and Clifford E. Herrick, In, Chenango Forks, N. Y., assignors to General Aniline & Film Corporation, New York, N. Y., a corporation of Delaware No Drawing. Application November 23, 1953, Serial No. 393,938

12 Claims. (Cl. 95-6) The present invention relates to a method of improving the rate of ammonia development of diazotype materials, and more particularly to the utilization of thiourea derivatives to compensate for adverse development con ditions in the ammonia developing chamber of dry developing machines.

It is recognized in the art that dry developing diazotype materials are those in which a base is coated with the sensitizing components comprising a light sensitive diazonium compound and a coupling component. Such materials are processed by exposure under a pattern followed by development of an azo dye image in the nonlight struck portions of the base, by treatment with ammonia vapors. By such treatment the undecomposed diazonium compound couples with the coupling component to produce the dye image.

It is customary to effect the exposure and development in one and the same machine containing an ammonia developing chamber. Usually the diazotype papers are formulated so that a satisfactory rate of image development is obtained with a normal concentration of ammonia in the ammonia developing chamber. However, conditions are often encountered in actual practice where the rate of ammonia feed to the ammonia developing chamber is too low to bring about a satisfactory degree of dye image formation, particularly if the print is developed at a high rate of speed, so that it spends only a few seconds in the developing chamber. Consequently, a need exists for dry developing diazotype materials which will show a satisfactory rate of image development under the adverse conditions of very low rate of ammonia feed to the ammonia developing chamber.

It has now been discovered that by including in the sensitizing formula for diazotype materials thiourea derivatives, in which one nitrogen atom bears a strongly negative group and the other nitrogen atom is strongly basic, it is possible to greatly accelerate the rate of azo dye color development under conditions of low ammonia concentration. The reason why these derivatives function as claimed has not been definitely established but appears to be attributable to their ability to form cationic complexes with the light sensitive diazonium compound in alkaline solution. Be that as it may, and regardless as to Whether our theory explained in greater detail hereinafter is correct, the fact remains that the use of such derivatives has been found to compensate for low ammonia concentration in dry developing machines, so as to ensure satisfactory development under such adverse conditions.

Light sensitive diazotype materials containing such thiourea derivatives and the processing of the same, particularly with low ammonia concentrations, constitute the purposes and objects of the present invention.

The thiourea derivatives, the use of which is contemplated herein, are those in which one nitrogen atom is trogen atom is strongly basic by reason of substitution by a radical of aliphatic character. Such compounds may be more precisely defined as having the following constitution:

iii

m which the ethylemc grouping forms part of an open hydrocarbon chain or part of an aromatic ring system, and B is in which R is an aliphatic radical, such as alkyl, i. e., methyl, ethyl, propyl, butyl, and the like, hydroxyalkyl, such as hydroxyethyl, hydroxypropyl and the like, alkoxyalkyl, such as methoxyethyl, ethoxyethyl and the like, and Z represents the atoms necessary to complete a fully saturated heterocyclic ring system such as morpholino, piperidino, pyrrolidino and the like. It is to be noted in passing that such heterocyclic ring systems, due to complete saturation, are strictly aliphatic in character.

The following compounds, embraced by the above formula, are found to be satisfactory for our purpose.

( I OH=CHCH1N C=S HOCHECHT-N 1-a1lyl-3-,B-hydroxyethyl-2-thiourea (2) lil CH==CHOH2N H; H: C-S 0 N C-C H2 H1 N-al1ylA-morpholinethiocarboxamide 5O 3 CH=OHCHz-N H H 0 -0 H2C\ /N C-C H2 H2 N-allyl-1-piperidylthiocarboxamide (4) 1-allyl-3-ethyl-2-thiourea (5 1-allyl-3-butyl-2-thiourea (6) 1-benzyl-3-fl-hydroxyethyl-Z-thiourea (7) 1-menaphthyl-3-p-hydroxyethyl-2-thiourea 1-al1y1-3 (2-hydroxypropyl) -2-tlnourea (9) l-benzyl-3 Z-hydroxypropyl -2-thiourea Most of the above compounds have been described in the literature. In any case, they can be prepared by the interaction of the appropriate isothiocyanate with the appropriate amine, and, in this connection, reference is made to the procedure given in copending application, filed on even date herewith by Ralph G. D. Moore, entitled l-benzyl-3-B-hydroxyethyl-Z-thiourea which discloses a typical method for preparing the involved compounds. This method is equally applicable to the compounds listed above.

It has been indicated that the thiourca derivatives are added to the sensitizing compositions. We have ascertained that the employment of such compounds in amounts ranging from 1 to 5% by weight of such compositions gives eminently suitable results.

In making up the sensitizing compositions we may employ any of the usual light sensitive diazonium compounds, and in this connection reference is made to the diazonium compounds mentioned in U. S. P. 2,501,874 and in the article by Van der Grinten Photographic Journal, vol. 923, 1952, page 46. It is understood, of course, that the diazonium compounds are preferably employed in the form of stable salts with zinc chloride, tin tetrachloride, cadmium chloride and the like according to customary practice. Examples of said diazos are those derived from N-dimethylamino-p-phenylenediamine; N- ethyl-N-B-hydroxyethyl-p-phenylenediamine; N-ethyl-pphenylenediamine; N-phenyl-p-phenylenediamine; N ,N diethyl 2 ethoxy p phenylenediamine; N ethyl 3- methyl-p-phenylenediamine; N,N-bisp-hydroxyethyl) -pphenylenediamine and N p hydroxyethyl N methylp-phenylenediamine and the like.

Coupling components usually employed in the manufacture of light sensitive diazotype materials are satisfactory for our purpose, and to this end we may employ resorcinol; S-methyl-l-phenyl-S-pyrazolone; 2,3-naphthalenediol; acetoacetanilide; Z-naphthol; 2-naphthol-3,6-disulfonic acid; 6,7 dihydroxy 2 naphthalenesulfonic acid; 8 hydroxy l-naphth[l,2]imidazole; 2,5 xylenol; 1,8- naphthalenediol; octylresorcinol and the like.

It will be observed from what has been said that neither the diazonium compounds, nor the coupling components, are critical factors in our invention.

The coating solutions may also contain the various adjuncts usual in the preparation of light sensitive diazotypc materials. These include metal salts for intensification of the dyestuff image, such as ammonium sulfate, nickel sulfate, zinc chloride and the like; stabilizing agents, such as thiourca, thiosinamine, naphthalene trisulfonic acid and the like; acids acting to retard precoupling, such as acetic acid, boric acid, tartaric acid and the like; hygroscopic agents such as glycol, glycerin and the like, and wetting agents such as saponin, lauryl sulfonate, kerylbenzene sulfonate, the oleic acid amide of N-methyltaurine and the like.

The sensitizing solutions are coated in a conventional manner by imbibition to a suitable surface, wiping off the excess with a glass doctor bar or other scraping device, and drying the base. Suitable bases are paper,

starch filled cloth, saponified cellulose acetate filmbase, cellulose acetate, cellulose acetate butyrate, ethyl cellulose and the like.

We have already noted that the beneficial effects derived from the utilization of the thiourca derivatives appear to be predicated upon the ability thereof to form cationic complexes with the diazonium compound in an alkaline solution. It is our firm belief that such complexes are actually produced, the following pattern being observed when the thiourca derivative is l-allyl-3-flhydroxyethyl-Z-thiourea and the diazo is derived from N,N-dimethyl-p-phenylenediamine:

ti-N=NON m Such complexes would appear to be more reactive toward azo coupling components than the diazotate, to wit:

usually formed when diazos are rendered alkaline in the absence of a developer accelerator. Assuming our hypothesis to be correct, it would be expected that an increase in the basicity of the nitrogen atom in 3-position, together with the presence of a group on the l-nitrogen atom which tends to enhance the formation of a mercapto group, would contribute to the complex forming tendency. Our data support this view in that the negative groupings which we have tried are effective substitutes on the l-nitrogen atom in causing the tautomerism indicated, whereas the groups of aliphatic character which are known to render nitrogen more basic produce effective results in the 3-position. Indeed, polarographic experimentation involving the behavior of diazo solutions containing, for example 1-allyl-3-fl-hydroxyethyl-2-thiourea, confirm the supposition that a complex is formed under alkaline conditions.

It is, of course, recognized that thiourca and certain derivatives thereof, such as thiosinamine, have been used as anti-yellowing agents in diazotype materials. Experimentation has established that the use of thiourca derivatives, such as thiosinamine in lieu of thiourca, would not provide sufficient advantages over thiourca to justify the employment of the derivatives for the purpose of decreasing yellowing, improving retention of dye density after development and improving dye brightness. Our reason for incorporating our thiourca derivatives into diam formulations lies in the fact constituting our discovery, to wit, that they greatly improve the rate of ammonia development by a factor of several times. Thus, even when the concentration of thiourca present in a control formula was increased by small increments up to and beyond a factor of 2, no improvement in development rate was achieved, whereas the incorporation of as little as 1% of our derivatives shows a substantial improvement in the rate of ammonia development. It might also be emphasized that our derivatives are capable of causing the color of the dye images obtained to become brighter and more pleasing to the eye, and to ensure that the brightness of the dye image remains over an extended period of time. However, these are inherent functions growing out of the use of the derivatives to improve rate of develop ment and are secondary in importance.

Thiourea is, itself, incapable of forming the complexes which we believe underlie the results which we obtain with the derivatives. Thus, polarographic experiments involving the behavior of diazo solutions with thiourca per se gave results far different from those obtained when using the thiourca derivatives contemplated herein.

The following examples will serve to illustrate the invention, parts being by weight unless otherwise stated. It is to be understood, however, that these examples are not limitative.

Example I A 100% sulfite paper sheet is imbibed in the usual manner with the following solution, the excess wiped off with a doctor bar and the paper dried.

Water to make 100 cc.

A sheet of the same paper was coated in the same way with the same composition, excepting that the 1-allyl-3- fl-hydroxyethy1-2-thiourea was omitted therefrom.

The two sheets were then exposed under a pattern and developed with ammonia vapor in an apparatus sold by General Aniline & Film Corporation of Johnson City, New York, under the trademark Ozalid Ozamatic dry developing machine. This machine has a developing tank capacity of 650 cubic inches and the normal rate of ammonia supplied is 2 quarts per day. The development herein, however, was elfected with a feed rate of 1 quart per day.

A comparison of the two prints made under identical conditions established that the print made while using the allyl thiourea derivative possessed a decidedly greater visual color density than that made without the allyl thiourea derivative.

As a matter of fact, it is not necessary even to resort to the dry developing machine in order to obtain a picture of the marked improvement effected by use of the allyl thiourea derivative. Thus, by treating sheets sensitized with the compositions previously referred to with a drop of ammonia applied to the center of each, it will be observed that on the sheet containing the allyl thiourea derivative, an immediate and rapid circle of development occurs which spreads outwardly from the drop. Development ensues at least several times as rapidly and is three or more times wider in area than the equivalent area on the control sheet.

Example II The following composition was prepared for application to a base in the manner subsequently indicated.

Water to make 100 cc.

The above solution is applied by a bead-coating technique to a 5000ths inch thick cellulose acetate film base at a rate of roughly feet per minute. (In the bead-coating technique the cellulose acetate foil is caused to pass across the surface of the solution in such a manner as to maintain contact therewith, and forming a meniscus about one inch in width on a six inch diameter roll, so that a thin uniform film of solution without runback is applied to the surface of the cellulose acetate.) A yellowish-brown color is obtained.

A control formula, identical with the above but containing no benzyl thiourea derivative, was treated in the same manner. Comparative prints showed that the first formula gave the same type of improvements as discussed in the previous example compared to a control sample without the benzyl thiourea derivative.

Example III The following composition was prepared for application to a base as subsequently indicated.

Water 0 Glycerin cc 5 Isopropyl alcohol cc 2 Tartaric acid grams 5 Zinc chloride do 5 1-allyl-3-fl-hydroxyethyl-2-thiourea do 2.5 8-hydroxy-1-naphth 1,2] imidazole do 2 p (N ethyl N B hydroxyethylamino)benzenediazonium chloride; zinc chloride complex grams 2 Saponin do 0.1

Water to make cc.

A 100% sulfite paper was coated with the above formula. The same type of paper was also coated with a control formula similar to the above formula in all ingredients, except that no allyl thiourea derivative was included. Prints made on the two papers showed the differences indicated in Examples I and II. A maroon color was obtained.

Example IV The procedure was the same as in Example I, excepting that the l-allyl-3-B-hydroxyethyl-2-thiourea was replaced by an equivalent quantity of N-allyl-4-morpholinethiocarboxamine. The results were substantially the same.

Example V The procedure was the same as in Example III, excepting that the 1-allyl-3-;3-hydroxyethyl-2-thiourea was replaced by 1-benzyl-3-fl-hydroxyethyl-2-thiourea. The results were substantially the same as those obtained in Example III.

Various modifications of the invention will occur to persons skilled in the art. Thus, it is evident that in lieu of the particular thiourea derivatives mentioned in the examples we may employ any of those contemplated by the above general formula, and particularly those referred to in the list given above. We, therefore, do not intend to be limited in the patent granted except as necessitated by the prior art and the appended claims.

We claim:

1. A dry developing light sensitive diazotype material comprising a base coated with a light sensitive diazonium compound, an azo dye coupling component and a thiourea derivative, capable of accelerating the rate of ammonia development of said light sensitive diazotype material after exposure thereof, one nitrogen atom of which is joined through a methylene group to a strong negative grouping of carbon atoms containing a C=C radical directly linked to said methylene group, and the other nitrogen atom of which is strongly basic by virtue of a chemical structure selected from the class consisting of those in which the nitrogen atom is substituted by an aliphatic radical and those in which the nitrogen atom forms part of a saturated heterocyclic ring.

2. The article as defined in claim 1, in which the thiourea derivative contains the following formula:

B in which the ethylenic grouping is contained in a hydrocarbon radical of the class consist- 7 ing of a straight chain of carbon atoms and an aromatic ring, and B is selected from the class consisting of H I IR and I N z in which R is an aliphatic radical and Z represents the atoms necessary to complete a saturated heterocyclic ring system.

3. The article as defined in claim 1, wherein the thiourea derivative is used in a concentration of 1 to 5% by weight of the sensitizing composition.

4. The article as defined in claim 2, wherein the thiourea derivative is used in a concentration of 1 to 5% by weight of the sensitizing composition.

5. The article as defined in claim 1, wherein the thiourea derivative is 1-allyl-3 3-hydroxyethyl-2-thiourea.

6. The article as defined in claim 1, wherein the thiourea derivative is 1-benzyl-3-t3-hydroxyethyl-Z-thiourea.

7. The article as defined in claim 1, in which the base contains thiourea per se as an anti-yellowing agent.

8. The process of producing prints from a light sensitive diazotype material comprising a base coated with a light sensitive diazonium compound and an azo dye coupling component which comprises exposing said light sensitive diazotype material under a pattern and developing the same with ammonia vapor in the presence of a thiourea capable of accelerating the rate of ammonia development, said thiourea having one nitrogen atom joined through a methylene group to a strong negative grouping of carbon atoms containing a C=C radical directly linked to said methylene group, and having as the other nitrogen atom one which is strongly basic by virtue of a chemical structure selected from the class consisting of those in which said nitrogen atom is substituted by an aliphatic radical and those in which said in which the ethylenic grouping is contained in a hydrocarbon radical of the class consisting of a straight chain of carbon atoms and an aromatic ring, and B is selected from the class consisting of and in which R is an aliphatic radical and Z represents the atoms necessary to complete a saturated heterocyclic ring system.

10. The process as defined in claim 8, wherein the thiourea is added in an amount of 1 to 5% by weight of the sensitizing composition.

11. The process as defined in claim 8, wherein the thiourea is l-allyl-3-p-hydroxyethyl-2-thiourea.

12. The process as defined in claim 8, wherein the thiourea is 1-benzyl-3-p-hydroxyethyl-2-thiourea.

References Cited in the file of this patent UNITED STATES PATENTS 2,487,034 Von Glahn et al Nov. 1, 1949 

1. A DRY DEVELOPING LIGHT SENSITIVE DIAZOTYPE MATERIAL COMPRISING A BASE COATED WITH A LIGHT SENSITIVE DIAZONIUM COMPOUND, AN AZO DYE COUPLING COMPONENT AND A THIOUREA DERIVATIVE, CAPABLE OF ACCELERATING THE RATE OF AMMONIA DEVELOPMENT OF SAID LIGHT SENSITIVE DIAZOTYPE MATERIAL AFTER EXPOSURE THEREOF, ONE NITROGEN ATOM OF WHICH IS JOINED THROUGH A METHYLENE GROUP TO A STRONG NEGATIVE GROUPING OF CARBON ATOMS CONTAINING A >C=C< RADICAL DIRECTLY LINKED TO SAID METHYLENE GROUP, AND THE OTHER NITROGEN ATOM OF WHICH IS STRONGLY BASIC BY VIRTUE OF A CHEMICAL STRUCTURE SELECTED FROM THE CLASS CONSISTING OF THOSE IN WHICH THE NITROGEN ATOM IS SUBSTITUTED BY AN ALIPHATIC RADICAL AND THOSE IN WHICH THE NITROGEN ATOM FORMS PART OF A SATURATED HETEROCYCLIC RING. 